Conventionally, a plunger type contact device B1 as shown in FIG. 15 is known (see for example Patent Document 1), which has a solenoid 102 configured to attract a plunger 102b due to magnetizing a stationary core 102a by applying electricity to a magnet coil 101. It has a pair of fixed contacts 103 that are connected to an external electric circuit. Furthermore, a movable contact 104 that is driven by the solenoid 102 so as to connect and disconnect the pair of fixed contacts 103 therethrough is disposed with a predetermined gap on the side opposite to the plunger relative to the pair of fixed contacts 103. The movable contact 104 is biased toward the fixed contacts by a pressing spring 105. Also, a space 107a which the fixed contacts 103 and the movable contact 104 are put in and a space 107b which the solenoid 102 is put in are separated by a diaphragm 106. Furthermore, at the center portion of the diaphragm 106, a bush 108 is inserted and fixed to the diaphragm 106. The bush 108 is disposed between the plunger 102b and the movable contact 104.
The bush 108 moves integrally with the movable contact 104 by a reactive force of a pressing spring 105, when the plunger 102b moves due to being attracted by the stationary core 102a, until the movable contact 104 moves to come in contact with the pair of fixed contacts 103. After the movable contact 104 comes in contact with the fixed contacts 103, the plunger 102b moves by itself separated from the bush 108 until it collides against the stationary core 102a. 
Also, in order to switch bidirectional currents of different magnitudes between conduction and cut-off, a plunger type contact device B2 as shown in FIG. 16 has been proposed (see for example Patent Document 2). The contact device B2 has a coil 201 that generates magnetic force by applying electricity, a pair of contact portions 202 that open and close in response to the magnetic force, and magnets 210 that are respectively disposed outside the pair of contact portions 202 adjacent thereto for extinguishing an arc by stretching the arc generated at the contact portions 202.
The pair of contact portions 202 have a pair of fixed holders 202a and a movable holder 202b. The fixed holders 202a are made of conductors that respectively hold the pair of fixed contacts 202c. The movable holder 202b is made of a conductor that advances and retreats with respect to the fixed holders 202a by a magnetic force generated by the coil 201, and a pair of movable contacts 202d are formed on the movable holder 202b so as to face the pair of fixed contacts 202c. 
Also, in order to extinguish an arc generated between the contacts in a short time, the magnets 210 for extinguishing an arc are provided, and an arc generated between the contacts is stretched by the magnets 210 for extinguishing an arc.
A movable core 203 is attracted toward a stationary core 204 by a magnetic flux that is generated when electricity is applied to the coil 201, and a shaft 205 and an insulator 206 attached integrally to the movable core 203 move together with the movable core 203. The movable holder 202b moves toward the fixed holder 202a together with the movable core 203 by means of a holder biasing means 205, and thereby the pair of movable contacts 202d come in contact with the pair of fixed contacts 202c. 
After the movable contacts 202d come in contact with the fixed contacts 202c, since the movable core 203 continues to be attracted toward the stationary core 204, the movable holder 202b and the movable core 203 are separated from each other at this time. Thereafter, the movable core 203 moves to the position where the lower end of the shaft 205 comes into contact with a bottom portion 207 provided inside the stationary core 204, and then comes to stop. At this time, the movable holder 202b is pressed toward the fixed holder 202a by the holder biasing means 205, the movable contact 202d is kept in contact with the fixed contact 202c, and a conduction state is formed between the contacts.